Stabilizing peroxygen compounds by enveloping in a water-dispersible layer

ABSTRACT

1. A PEROXYGEN-CONTAINING COMPOSITION CONSISTING ESSENTIALLY OF A PARTICULATE NORMALLY UNSTABLE PEROXYGEN COMPOUND AND A WATER DISPERSIBLE LAYER OF FROM 1% TO LESS THAN 15% BY WEIGHT, BASED ON THE WEIGHT OF THE LAYER AND OF THE PEROXYGEN COMPOUND, OF A SOLID WATERINSOLUBLE COMPOUND SELECTED FROM THE GROUP CONSISTING OF (1) FATTY ACIDS OF GREATER THAN 8 CARBON ATOMS, (2) ALKANOLAMIDES OF FATTY ACIDS OF AT LEAST 8 CARBON ATOMS, (3) GLYCEROL ESTERS OF FATTY ACIDS OF AT LEAST 8 CARBON ATOMS, (4) LONG-CHAIN ALIPHATIC HYDROCARBON ALCOHOLS, AND (5) PARAFFIN WAXES, THE LAYER ENVELOPING THE PARTICLES OF PEROXYGEN COMPOUND AND AT LEAST PARTIALLY STABILIZING THEM TO DECOMPOSITION.

US. Cl. 252-186 12 Claims ABSTRACT OF THE DISCLOSURE Normally unstable peroxygen compounds Which but for their unstable properties would find use in heavy duty household detergents are stabilized by enveloping particles of the unstable oxygen compound with a water dispersible layer of from 1% to lessthan by weight of a solid water-insoluble compound selected from the group consisting of (1) fatty acids of greater than 8 carbon atoms, (2) alkanolamides of fatty acids of at least 8 carbon atoms, (3) glycerol esters of fatty acids of at least 8 carbon atoms, (4) long-chain hydrocarbon aliphatic alcohols, and (5) parafiin waxes, the layer enveloping the particles of peroxygen compound and at least partially stabilizing them to decomposition.

This invention relates to particulate peroxygen compounds for example alkali metal percarbonates and perphosphates, and to detergent mixes containing such compounds.

It is well known that peroxygen compounds can be employed in a detergent mix as bleaching compounds. At present domestic heavy duty detergents usually employ sodium perborate tetrahydrate as a bleaching compound because it is relatively stable to decomposition in a detergent environment. It is becoming more common to use cool washing and soaking techniques and sodium perborate tetrahydrate has the disadvantage of a relatively low solution rate at C. It has been proposed to use admixtures of base detergents with many other inorganic peroxygen compounds, including adducts of alkali metal salts often present in base detergent compositions, such as alkali metal carbonates and phosphates, with hydrogen peroxide, which adducts do have suitable rates of solution. Decomposition of such adducts however, is accentuated at ambient temperatures, by relative humidities of greater than about 40% which humidities are often generated by commercially available base detergents, thereby lowering the bleaching effect of the detergent mix.

Previously attempts have been made to overcome the problems of instability of unstable peroxygen compounds by admixing the peroxygen compound with inorganic salts acting as stabilisers, for example, sodium or magnesium salts, including sodium or magnesium silicate, sulphate, chloride and nitrate, or admixing with ammonium or alkali metal pyrophosphate and an organic sequestering agent, for example ethylene diamine tetraacetic acid (E.D.T.A.). These admixtures have not proven wholly successful for use with inorganic percarbonate or perphosphates, because significant decomposition still occurs on storage.

The present invention provides a peroxygen containing composition comprising a particulate normally unstable peroxygen compound and a water-dispersible layer consisting of less than 15% by weight, based on the weight of the layer and of the peroxygen compound, of a water ted States Patent Oil ice Patented Nov. 12, 1974 insoluble agent, the layer enveloping the particles of peroxygen compound and at least partially stabilising them to decomposition.

By the term water dispersible layer is meant a layer which is sufficiently dispersible, under the conditions of the following test, to allow the peroxygen compound which has been enveloped to dissolve to the extent of by weight in not more than 30 minutes and preferably in less than 15 minutes.

The test comprises placing 2 g. of enveloped peroxygen compound in 1 litre of water maintained at 15 C. and stirring continuously. The time for 75% by weight solution is measured by known means.

Dissolution times of an enveloped peroxygen compound in water bears a close relationship to the dissolution times of the same enveloped peroxygen compound in the aqueous phase of many commonly-used washing media.

Advantageously the agent from which the layer is formed is compatible with the peroxygen compounds in solution, does not affect the performance of other components present in detergent compositions and absorbs little or zero water in atmospheres of high humidity. Desirably the agent is a compound which could advantageously be incorporated in detergent mixes.

It has been found that suitable agents are fatty acids, and glycerol esters and alkanolamide derivatives of such acids. Preferably the fatty acids, which can be either natural or synthetic, contain from 8 to 26, particularly 10 to 24 especially 12 to 22 carbon atoms. Preferably the fatty acids are hydrogenated, and particularly have an iodine number lower than 30. Mixtures of hydrogenated fatty acids derived from coconut oil, tallow oil, castor oil or groundnut oil are especially suitable.

Suitably the alkanolamide derivatives are monoalkanolamide derivatives, or those dialkanolamide derivatives having a melting point at not less than 35 C. preferably of not less than 40 C.

Preferably the alkanolamide radical contains not more than 6 carbon atoms, for example, ethanolamide or propanolamide.

Long chain aliphatic alcohols, for example cetyl alcohol or stearyl alcohol or polyvinyl alcohols, or paraflin waxes may be used as enveloping agents, according to other embodiments of the invention.

By the term normally unstable peroxygen compounds is meant solid organic peroxygen compounds, inorganic peroxymonosulphates, and adducts of inorganic salts with hydrogen peroxide, which have poor stability to decomposition at ambient temperatures when in admixture with a solid base detergent composition containing at least 10% by weight water based on the composition, this often being sufficient water to generate in a sealed container a relative humidity of at least approximately 40%. In a test for stability of the peroxygen compound, a detergent composition containing, by weight, based on the composition, at least 2.0% of an active linear alkyl benzene sulphonate, at least 30% sodium tripolyphosphate and at least 10% water may suitably be used. Often at least 15 to 20% of the peroxygen compound may decompose after storage for one year under the above stated conditions, in comparison with sodium perborate tetrahydrate, which, under similar conditions, has a decomposition of about 1 to 3%.

Herein, percentages of decomposition are by weight based upon the weight of the peroxygen compound, and excluding the weight of the agent.

The invention is particularly suitable for treating solid peroxygen compounds which suffer at least 30% decomposition after storage for 1 year at ambient temperatures in admixture with a major proportion of a synthetic base detergent containing at least by weight water, 20%- 25%, by weight active linear alkyl benzene sulphonate and 30%-35% sodium tripolyphosphate, and which admixture has an active oxygen content of 1% The active oxygen content of an admixture is dependent upon the active oxygen content of the peroxygen compound in the admixture. Admixtures of peroxygen compounds with synthetic base detergents often have active oxygen contents of from to 3% by Weight based on the admixture. It has been found that as the percentage of sodium percarbonate, in such an admixture is increased then the sodium percarbonate decomposes at a slower rate. Thus the percentage loss of active oxygen content based on that present initially, falls as the percentage of sodium percarbonate in the admixture is increased.

Suitably the adducts of inorganic salts with hydrogen peroxide may be adducts of alkali metal salts with hydrogen peroxide. Preferably such alkali metal salts are salts often present in many detergent compositions such as alkali metal carbonates or phosphates, particularly sodium salts. The adduct of a salt is referred to herein as a persalt. Especially preferred persalts are sodium percarbonate (Na CO A H O sodium perpyrophosphate and sodium pertripolyphosphate.

Preferably the inorganic peroxymonosulphate is that of an alkali metal, especially potassium.

Preferably the organic peroxygen compound may be an organic peroxyacid, preferably having a melting point above 50 C., for example, a peroxyphthalic acid or a substituted peroxybenzoic acid.

Preferably inorganic peroxygen compounds which have a high active oxygen content, for example sodium percarbonate having approximately 13.5% by weight, and those which have good solubilities in detergent solutions, are used.

It is disadvantageous for the packet life of a peroxygen compound in a detergent environment to be short. Enveloping normally unstable peroxygen compounds in a layer of a water insoluble agent reduces their instability by creating, it is believed, a physical barrier to water transfer. It has been found that for layers applied using the same method, a relationship exists between the weight percentage of enveloping agent applied hereinafter referred to as level of envelopment and the stability of the peroxygen compound in the detergent environment.

Although the rate of solution of a peroxygen compound enveloped in a layer of water insoluble agent according to the invention is slower than that rate of the unenveloped peroxygen compound of corresponding particle shape, size range and chemical constitution, surprisingly it has been found that a suitable rate of solution at ambient temperatures can be obtained, provided that the weight percent of water insoluble agent applied is according to the invention. Surprisingly it has been found that such a layer is readily dispersed in aqueous washing media at temperatures below its melting point. Enveloping the peroxygen compounds in such a layer can both protect against decomposition induced by humid air, and also release the peroxygen compound in aqueous washing media at ambient temperatures. An inverse relationship exists between the rate of solution at a temperature of for example C. of an enveloped peroxygen compound and the level of envelopment, when the envelopment is applied using the same method. At levels of envelopment higher than those according to the invention, rates of solution of the enveloped peroxygen compound at ambient temperatures may not be high enough for advantageous use in cold washing or cold soaking, and may in extreme cases ap proach zero. Thus there exists for each particulate peroxygen compound an optimum range or ranges of levels of envelopment within which the apparently contradictory conditions of much enhanced stability and thereby longer packet life, and also a suitable rate of solution at ambient temperatures are fulfilled, depending upon which method of application of the envelopment is empl y Suitably particles having any shape or size may be enveloped, but particles having a higher ratio of surface area to volume require a higher level of envelopment to produce a layer allowing similar rates of solution and similar packet stability of the enveloped peroxygen compound. As the particles become less regular, or become smaller their surface area/volume ratio rises. Thus, preferably, particles to be enveloped have a fairly narrow range of particle sizes, or have a similar iregularity of shape.

Particularly suitably the particle size range may be from approximately to about 1000 especially suitably the particles may be approximately spherical.

Preferably the layer contains from 1% to 10% by weight based on the enveloped peroxygen compound of a water insoluble agent. A particularly preferred range of levels of envelopment depend upon how evenly the envelopment is applied, the more even the envelopment, in general, the lower the preferred range.

If the method of application is to deposit the agent from solution onto the particulate peroxygen compound, the preferred level of envelopment is from 1% to 5% by weight based on the enveloped peroxygen compound. If the layer is applied by contacting molten agent with the particulate peroxygen compound the preferred level of envelopment is from 4% to 10% by weight based on the enveloped peroxygen compound. Use of an improved molten agent application technique might lower the preferred range.

Suitably one or more layers of enveloping agent may be applied, or a mixture of agents may be applied, provided that the total level of envelopment does not exceed 15% by weight. Successive layers may be applied using similar or different methods.

Particles to be enveloped may be produced by, for example, a solution process or a fluidised bed method, and may or may not have been classified.

As a result of enveloping the particles at the same level of envelopment by different methods for example, methods 1 to 5, described hereinafter, the flow properties, packet stability and solution rate of the enveloped particles of similar shape and size may vary.

Method 1.-The particles are immersed in a bulk solution of an enveloping agent in an organic solvent, for example, a paratlin wax in carbon tetrachloride, followed by filtration, and evaporation of the solvent. In a variation the filtration step may be omitted.

Method 2.-A solution of enveloping agent in a solvent, for example, tallow acid monoalkanolamide in methanol is sprayed onto the particles agitated in a fluidised bed, the bed being supplied continuously with enough hot air to evaporate off the solvent.

Method 3.Hot molten enveloping agent, for example, molten lauric acid monoalkanolamide is sprayed onto the particles agitated in a non-heated fluidised bed, and allowed to cool.

Method 4.Hot molten enveloping agent is sprayed onto the particles agitated in a fluidised bed heated to a temperature of at least that of the melting point of the enveloping agent. After agitation the bed is cooled by the use of a cool fluidising gas.

Method 5.Hot molten enveloping agent is added in bulk to a hot bed of the particles, and agitated mechanically, for exampe, in a Lodige-Morton mixer, and then allowed to cool.

For enveloping peroxygen compounds whose melting points are lower than those of the enveloping agents Methods 1, 2 and 3 are preferable, Method 2 yielding a particularly suitable product. For enveloping peroxygen compounds whose melting points are higher than those of the enveloping agents, Methods 2, 4 and 5 are particularly suitable, Methods 2 and 5 preferable.

The invention will now be illustrated by means of the following examples, which in no Way define the scope of the invention.

Examples 1, 13, 15 and 17 are inserted for purposes of comparison only.

Examples 2 to 12, 14, 16 and 18 are according to the invention.

The peroxygen compound used in Examples 1 to 12 was particulate sodium percarbonate, unenveloped and having a range particle size of from 120 to 1000 prepared by a fluidised bed process as described in copending British application 32,640/70 followed by granulation.

The enveloped peroxygen compound used in Examples 2-12 was prepared by enveloping the particulate sodium percarbonate in a water-insoluble fatty acid alkanolamide at a level of envelopment indicated in the following table. In Examples 2, 3, 4 and 8 the sodium percarbonate particles were enveloped in Empilan CME, in Examples 5, 6, 7 and 9 in Ethylan LM, in Example 10 in Empilan TME, and in Examples 11 and 12 in Ethylan LMP.

In Examples 2 to 7 20% solution by weight referred to the solution of fatty acid alkanolamide in methanol was sprayed on to a bed of sodium percarbonate particles, fluidised by the passage of hot air, the temperature of which bed was maintained at between 27 C. and 35 C. The hot air evaporated off the methanol, leaving the persalt particles enveloped in a fatty acid alkanolamide.

In Examples 8, 9 and 11 the enveloping agent was melted and then sprayed onto sodium percarbonate particles agitated in a fluidised bed through which air at ambient temperatures was forced.

In Example 10 the enveloping agent was melted and then sprayed onto sodium percarbonate particles agitated in a fluidised bed through which air, maintained at a temperature of a few degrees above the melting point of the enveloping agent was forced.

In Example 12 the enveloping agent was applied in two layers. The first layer was applied using the method used in Example 11, the level of envelopment being 9% by weight. The second layer, by weight, was applied using the same method used in Example 10.

In Examples 13 and 14, the peroxygen compound was a different sample of particulate sodium percarbonate prepared by a fluidised bed process as described in German Oifenlegungsschrift No. 2,060,971, followed by granulation.

In Examples 15/16, and 17/18, the peroxygen compounds were two samples of particulate sodium percarbonate prepared by a fixed bed process, in which sodium carbonate and aqueous hydrogen peroxide and suitable stabilisers are mixed, and sodium chloride added to the resultant solution with cooling to precipitate out sodium percarbonate granules which are centrifuged, and then dried in a rotary drier.

In Examples 14 and 16 the persalt particles were enveloped in Empilan CME by adding molten Empilan CME in bulk to a bed of persalt particles having the temperature of about 65 C., and agitating mechanically in a Lodige-Morton mixer for about 8 minutes, and then allowed to cool.

In Example 18 the peroxygen compound was enveloped in paraffin wax by immersion of the peroxygen compound in a bulk solution of paraflin wax in carbon tetrachloride, followed by evaporation of the carbon tetrachloride.

Empilan TME is a trademark for a commercial preparation of tallow acid monoethanolamide (M.P. 72.8 C.) made by Marchon Division of Albright & Wilson Limited.

Empilan CME is a trademark for a commercial preparation of coconut oil acid monoethanolamide (M.P. 67.5 C.) made by Marchon.

Ethylan LM is a trademark for a commercial preparation of lauric acid monoethanolamide (M.P. 55.5 C.) made by Lankro Chemicals Limited.

Ethylan LMP is a trademark for a commercial preparation of lauric acid monoethanolamide (M.P. 55.5 C.) made by Lankro.

TEST FOR SOLUTION RATE IN WATER In each of Examles 13, 15 and 17, 2 grams of unenveloped particulate sodium percarbonate were placed in 1 litre of water maintained at a temperature of 15 C. and stirred constantly to ensure good mixing. The electrical conductivity of the resultant solution was measured using a conductivity cell and Wheatstone bridge, and time taken by the solution to reach the same conductivity as that exhibited by a solution of 1.5 grams/ litre of particulate sodium carbonate is the time shown in the table for 75% solution. In each of Examples 2 to 12, 14, 16 and 18, a solution of 2 grams/litre of enveloped sodium percarbonate particles prepared by the methods as described hereinbefore was tested in a similar manner by measuring the time taken by that solution to reach the same conductivity as that. of a 100% solution of 1.5 grams/litre of that same enveloped sodium percarbonate.

TEST FOR PACIQET STABILITY To determine the packet stability in a detergent environment, of the enveloped peroxygen compounds prepared above, a portion of each peroxygen compound was blended with a synthetic base detergent which had been pre-equilibrated at 44% relative humidity at 30 C. for at least 3 days and contained then 10% by weight of water, by passing the mixture through a Pascal Rotary Sample divider. The enveloped percarbonate particles contained initially approximately 12% by weight available oxygen, and the blend of detergent base and enveloped percarbonate contained 8% by weight of enveloped percarbonate.

Each of the blends contained approximately 1% by weight available oxygen initially, which percentage was determined accurately by dissolving completely a known weight of detergent in a dilute aqueous sulphuric acid solution and titrating the resulting solution against a potassium permanganate solution of known normality. The blend used in Example 1 contained unenveloped sodium percarbonate particles and pre-equilibrated base detergent, and the blend used in Examples 2 to 7 contained base detergent and sodium percarbonate particles enveloped at a level shown in the table.

The blends were sealed in glass jars and stored at ambient temperatures, which varied between 19 C. and 28 C. but usually between 19 and 24 C.

10 grams of each blend were withdrawn monthly by subdividing the whole blend in the sample divider and returning the remainder unused to the sealed container. The percentage active oxygen content of each blend was determined by employing a similar method to that used before and from the knowledge of initial and final active oxygen contents of each blend, the percentage decomposition of the percarbonate determined.

The details of Examples 1 to 12 are summarized in the table (col. 7).

On the one hand, it would be expected that for particulate normally unstable peroxygen compounds to gain much improved stability, such particles would need to be substantially completely covered by a layer of water insoluble agent. Such a layer would be expected to be equally eflicient in aqueous media, and thus prevent the peroxygen compound dissolving at a reasonably fast rate at temperatures below the melting point of the water insoluble agent.

On the other hand, particles only partially covered would be expected to have both a reasonably fast solution rate and also little improvement in stability.

From the table it may be seen that, most surprisingly, a combination of much improved stability to decomposition, and reasonable solution rate at ambient temperatures can be achieved, provided that the layer is according to the present invention.

TABLE Enveloping agent Time Percent decomposition for 75% solution in After 3 After After 9 Percent minutes months months months Ex. N0 Substance by wt. at C.

1 0. 9 32 48 2 Empilan CME 1.7 3.6 6.1 15 3 -d0 2. 8 7. 8 0 2.0 8 4 "do 4. 3 12.4 0 0 6 5- Ethylan LM 1.7 2.3 3.6 5. 2 17 6 do 4. 0 4. 7 0 0 3 7- o 4.4 10.0 0 0 5 8. Empilan OME 10 2.2 10.2 18 9. Ethylan LM 10 1. 25 15. 6 23 10..- Empilan TME 15 10.0 3.8 7 13 11 Ethylan LMP 9.0 8. 05 9. 6 16 24 12 do 14. 0 5.85 2.0 5 10 The invention claimed is:

1. A peroxygen-containing composition consisting essentially of a particulate normally unstable peroxygen compound and a water dispersible layer of from 1% to less than 15% by Weight, based on the weight of the layer and of the peroxygen compound, of a solid waterinsoluble compound selected from the group consisting of (1) fatty acids of greater than 8 carbon atoms, (2) alkanolamides of fatty acids of at least 8 carbon atoms, (3) glycerol esters of fatty acids of at least 8 carbon atoms, (4) long-chain aliphatic hydrocarbon alcohols, and (5) paraffin waxes, the layer enveloping the particles of peroxygen compound and at least partially stabilising them to decomposition.

2. A peroxygen containing composition as claimed in claim 1 wherein the peroxygen compound is selected from the group consisting of alkali metal percarbonates, alkali metal perpyrophosphates, alkali metal pertripolyphosphates and alkali metal peroxymonosulphates.

3. A peroxygen containing composition as claimed in claim 2 wherein the peroxygen compound is sodium percarbonate.

4. A peroxygen containing composition as claimed in claim 1 wherein the peroxygen compound is an organic peroxyacid.

5. A peroxygen containing composition as claimed in claim 1 wherein the layer consists of from 1% to 10% by weight base of water insoluble agent.

6. A peroxygen containing composition as claimed in claim 1 wherein the water-insoluble compound is a fatty acid containing from 8 to 26 carbon atoms.

7. A peroxygen containing composition as claimed in claim 6 wherein the fatty acid is saturated.

8. A peroxygen containing composition as claimed in claim 1 wherein the water-insoluble compound is an alkanolamide of a fatty acid of at least 8 carbon atoms, said alkanolamide having a melting point of not less than 35 C.

9. A peroxygen containing composition as claimed in claim 8 wherein the alkanolamide radical consists of not more than 6 carbon atoms.

10. A method of at least partially stabilising a normally unstable particulate peroxygen compound comprising at least partially enveloping the particles in a water-dispersible layer of a solid water-insoluble compound selected from the group consisting of 1) fatty acids of greater than 8 carbon atoms, (2) alkanolamides of fatty acids of at least 8 carbon atoms, (3) glycerol esters of fatty acids of at least 8 carbon atoms, (4) long-chain aliphatic hydrocarbon alcohols, and (5) paraffin waxes, said compound comprising from 1 to less than 15% by weight based on the weight of the enveloped particulate peroxygen compound.

11. The method of claim 10 wherein the layer is deposited from solution and consists of from 1% to 5% by weight of water-insoluble agent, based on the enveloped peroxygen compound.

12. The method of claim 10 wherein the layer is prepared by contacting molten agent with the particulate peroxygen compound, and consists of from 4% to 10% by weight based on the enveloped peroxygen compound of agent.

References Cited UNITED STATES PATENTS 3,650,963 3/1972 Werdehausen et a1. 252-186 3,658,712 4/1972 Lindner et al. 252186 3,666,680 5/1972 Briggs 252186 CARL D. QUARFORTH, Primary Examiner I. GLUCK, Assistant Examiner US. Cl. X.R.

81ll; ll7-l00 A, B; 25295, 102, 383, 384; 2606l0 A; 423-272 

1. A PEROXYGEN-CONTAINING COMPOSITION CONSISTING ESSENTIALLY OF A PARTICULATE NORMALLY UNSTABLE PEROXYGEN COMPOUND AND A WATER DISPERSIBLE LAYER OF FROM 1% TO LESS THAN 15% BY WEIGHT, BASED ON THE WEIGHT OF THE LAYER AND OF THE PEROXYGEN COMPOUND, OF A SOLID WATERINSOLUBLE COMPOUND SELECTED FROM THE GROUP CONSISTING OF (1) FATTY ACIDS OF GREATER THAN 8 CARBON ATOMS, (2) ALKANOLAMIDES OF FATTY ACIDS OF AT LEAST 8 CARBON ATOMS, (3) GLYCEROL ESTERS OF FATTY ACIDS OF AT LEAST 8 CARBON ATOMS, (4) LONG-CHAIN ALIPHATIC HYDROCARBON ALCOHOLS, AND (5) PARAFFIN WAXES, THE LAYER ENVELOPING THE PARTICLES OF PEROXYGEN COMPOUND AND AT LEAST PARTIALLY STABILIZING THEM TO DECOMPOSITION. 